Electrical condenser



May 7, -1935.

W. COLVIN, JR

ELECTRICAL coNDENsER Filed Feb. 19, 1951 M7/ iam Co/w'n Jr: @MW/WZ( A Trae/w: Ys

Patented May 7, 1935 UNITED STATES 'PATENT OFFICE comms.

My invention relates to electrical condensers and more particularly to electrical condensers adapted to vibrate in response to variations in voltage produced in an associated electrical circuit, thereby producing audible sound waves.

While in the following I refer to my invention as a receiver` or loudspeaker, it is to be understood that in so doing I merely describe and illustrate a specific application thereof and am in no way limited to this particular use of my invention.

A majority of receivers or loudspeakers, in present day use by the public, operate on an electromagnetic principle. To attain results commensurate therewith, and to eliminate the plurality of parts entailed in the construction of speakers operating on the electromagnetic principle, I have designed a speaker to operate on an electro-static principle. Furthermore, my invention contemplates an electrical condenser which may be used either for transmitting or reproducing sound waves and which is of such character that it is particularly susceptible to concealment or disguise as a picture or part of the wall of a room or building. One very useful application will be projecting screens for moving pictures which are accompanied by sound effect and in which the sound can actually be made to emanate from the screen itself.

I accomplish these results by the novel elements and the combinations and arrangements thereof described below and illustrated in the accompanying drawing, in which Fig. 1 is a perspective view of my device, partly broken away for further illustration;

Fig. 2 is a fragmentary face view greatly enlarged ofa wire fabric element;

Fig. 3 is a fragmentary sectional view illustrating a method of mounting the elements with relation to each other;

Fig. 4 is a view similar to Fig. 3 showing the elements mounted in a modied form;

Figs. 5, 6, 7 and y8 are diagrammatic illustrations of modified forms of my invention; and

. Fig. 9 is, a wiring diagram illustrating my invention with respect to the associated electrical circuit.

Like reference characters vindicate like parts throughout the drawing.

Though the elements of an electrical condenser, as commonly understood, consist of a plurality of metallic plates separated by a dielectric medium, I have described and illustrated my invention as applied to or used as a receiver or sound-producing device, although it may be used as a condenser for transmitting sound waves by radiant energy, or in connection with any electrical apparatus where a condenser is necessary.

Referring now to the drawing, I have illustrated in Fig. 1, one embodiment of my device indicated generally at I. 2 is a frame made of any suitable material such as wood, metal, bakelite .or the like, and though illustrated as rectangular,

may be constructed in any desired shape. Within frame 2 is a second frame 3, mounted and adjustably secured with respect to the outer frame 2 by means of bolts 4. The side members of frame 3 (see also Figs. 3 and 4) are comprised of two members, a bar member 5, through which bolts 4 pass, and an auxiliary bar 6, secured to bar 5 by means of Abolts 1. The two bar members form a clamping device adapted to hold the wave-producing elements of my invention in position. Bolts 4 may be inserted through the side members of frame 2 to engage with threaded openings in frame 3 or, of course, an alternative method may be used whereby bolts 4 are secured to frame 3 and pass through the outer frame 2, in such case being adjustably secured as by wing nuts or in some other adequate manner. It is to be understood that the sides of the inner frame member 3 are in no manner connected at their ends to the adjacent side members, hence, when the wing nuts are turned in one direction or another and the sides-of frame 3 being free to move with respect to each other, any member or plurality of members placed within said inner frame 3 and clamped thereto, may be placed under substantially any degree of tension desired.

I do not wish to limit myself to the tension frame as described above, for any suitable device may be used whereby an even or uniform tension may be applied to the elements placed therein.

The elementary parts utilized in the construction of the receiver or loudspeaker operated on an electro-static principle consist of two plates, mounted in parallel, spaced relationship to each other and separated by a dielectric medium. One

of the plates should be supported, with some degree of rigidity and the other, generally known as a diaphragm, should be allowed to vibrate with respect thereto. Hence, the principle of operation is equivalent to an electric condenser comprising plates, one of which is slightly movable with respect to the other, necessitating, when this type of loudspeaker is incorporated in a receiving circuit, a comparatively high voltage being impressed across the two elements or plates. With the usual type of radio receiver, a sound wave of radio frequency is received, demodulated, and

then amplified as an audio frequency wave. To the output of the last stage of audio amplification is connected the loudspeaker or receiver. In the electrostatic type of speaker, the demodulated and transformed wave varies the charge on the plates, which in turn causes a variation in mechanical stress between the plates so that the diaphragm or movable plate vibrates producing sound waves.

In my invention, I utilize a plate element of flexible material generally represented at I0, having a current carrying capacity, which may be used either as the rigidly fixed plate or as the movable diaphragm. In Fig. 2, I have shown a highly magnified fragmentary portion of the element. 8 represents parallel disposed wires, composed of any suitable current carrying metal, preferably covered with an insulating lacquer 9, and enclosed by insulation 91, peferably of cotton, silk, or like material. Wires 8 are held in spaced relationship by means of a fabric within which they are woven, said wires in the fabric illustrated, forming the weft, and strands forming the warp. Strands II may be of any weavable material, such, for example, as cotton, wool, silk, rayon, etc. An additional strand I2 is interwoven with the wires 8 and strands I I along their lines of contact, whereby a resultant, fairly closely woven fabric is formed, and in which the wires are very uniformly spaced. A fabric which is particularly well adapted for use in this invention is disclosed and claimed in my copending application Serial Number 471,758.

In one assembly of my loudspeaker illustrated in Fig. 3, the wire interwoven fabric III used as a plate element is securely clamped within the inner frame member 2 of the tension device. The parallel spaced wires are electrically connected together atvone end and, collectively, form one plate or element of the loudspeaker. To one face of my fabric is secured, by means of an adhesive substance, I4, a thin sheet of metallic material, I3, such as aluminum foil or the like, and this foil constitutes the second plate of my loudspeaker. By adjusting the inner frame, 3, through the operation of bolts, 4, fabric III may be placed under any desired tension, both longitudinally or transversely thereof, thus retaining it in comparatively rigid relation to the foil. Thus, in the embodiment of my invention above described, fabric I0, constitutes the fixed plate member and the metallic foil, I3, the diaphragm or movable plate. The dielectric spacing therebetween is dened by the amount of insulation on the wires and that portion of the fabric plus the adhesive substance which separates the two plate elements.

In Fig. 4 I have illustrated a modification of the species of my invention shown in Fig. 3 which produces somewhat better results. A nely woven elastic fabric I5, preferably of silk, is interposed between the wire woven fabric, I0, and the metallic foil, I3, andfto which said metallic foil is secured in the manner above described. The advantage derived with Ithis assembly is, that a more elastic medium is provided between the plates, producing a finer quality of tone production.

Of course, the novel wire interwoven fabric, IB, in that it forms a plate element, may be substituted for the metallic foil or its equivalent, as shown in Fig. 5. Here, both plates are formed with wire interwoven fabric, I0, separated by a nely woven silk fabric, |5I, one wire interwoven fabric, as lili, forming the fixed plate member and the other, |02, acting as the vibrating dlaphragm. This specific type of construction seems to produce the best results.

In Fig. 6 a further modification is shown, whereby I utilize, as the fixed element, a substantially rigid plate, |6, of suitable metal such as steel or the like. Plate i6 is rigidly fixed in non-vibrating position and is separated by a finely woven silk fabric, |52, from the wire interwoven element |03. Element |03 lies smoothly across the faces of plate I6 and in engagement with the separating elastic medium, |52, of silk.

Fig. 7 illustrates a modification similar to that shown in Fig. 6. However, in this assembly, the wire interwoven fabric Illlis mounted in close relationship to the face of the non-vibrating plate element, IBI, and no additional separating medium is used, the material of the .fabric itself providing the separating and substantially elastic dielectric medium between the wires and the plate element.

In Fig. 8, I have represented two metallic plate elements, either of which is interchangeable with the plate elements hereinbefore described. The xed, non-vibrating plate, |62, is separated by a finely woven/fabric, |53, from the second plate, Il, which may consist of metallic foil or the like adhering to or held in close engagement with fabric, |53.

From the foregoing description, it is to be understood that I attain a 'condenser effect by employing the wire interwoven fabric in combination with another likefabric or its electrical equivalent. The various plate elements may be used interchangeably and with or without an additional separating medium, provided, of course, they are insulated from each other. It is de. sirable to mount the said elements in close proximity, the one with the other and to interpose an elastic medium therebetween, to the end that the speaker will be operable with a minimum power input. The interposition of an elastic medium such as a thin sheet of silk, between the plates seems to eliminate distortion to a great extent in the emanating sound waves and very greatly improves the reproduction.

When used as a speaker, my condenser is connected in the secondary circuit I3 of an output transformer inv the usual manner as illustrated in Fig. 9, the plate of the last audion or amplifying tube I9 being connected to the primary winding of thetransformer, all of which is well known in the art. Though I have illustrated a radio circuit, my speaker may, of course, be used with any other method of voice transmission whereby electrical energy is used as a carrier means.

In that my device does not depend on its size or magnitude for efliciency or tone production, I may construct it of any desired size; the larger in surface area, the greater is the power input required to operate it and, of course, the volume output varies therewith. Hence, my device is admirably adapted for ornamental and unique purposes for which electromagnetic speakers would be poorly suited. A

While I have described my invention in its preferred embodiments, it is to be understood that the words which I have used are words of description and not of limitation and that changes within the purview of the appended claims may be made without departing from the true scope and spirit of my invention in its broader aspects.

. What I claim is:

l. As a new article of manufacture, a combined plate element and dielectric for an electrical condenser comprising closely-spaced, separately insulated conductors interwoven with textile threads and forming a fabricated plate element.

2. As a new article of manufacture, an electrical condenser having a plate element comprising a woven fabric having electrical conductors interwven therewith; said plate element presenting totally insulated surface areas.

3. As a new article of manufacture, a plate element for an electrical condenser comprising a fabric lhaving electrical conductors interwoven therewith, said conductors being each insulated independently of said fabric;` said plate element being air pervious and comparatively loosely woven to permit independent movement of said conductors.

4. A plate element for a loud speaker of the condenser type comprising a fabric having individually-insulated, metallic conductors incorporated therein; the insulator for each of said conductors Lforming an integral part of said fabric.

5. As a new' article of manufacture, a plate element for a. 4loud speaker of the condenser type, said plate element comprising a plurality of spaced electrical conductors, each of said conductors being enclosed in a separate insulating medium and a second insulating medium' securing said insulated conductors in uniform spaced relationship.

6. As a new article of manufacture, a plate element for an electrical condenser comprising a plurality of threads or yarns having ne metal wire cores enclosed in firm wrappings of fibrous insulating material; said wrappings forming a comparatively elastic dielectric.

. WILLIAM COLVIN, Jn. 

